Histone N-terminal tails maintain chromatin stability and are subject to modifications associated with transcriptional regulation. The best characterized of these modifications are acetylation, methylation and phosphorylation For each modification, enzymes exist that either lay down the appropriate mark or remove it. These modifications must then be interpreted by the transcriptional machinery. Acetyl-lysine recognition is principally mediated by bromodomains, which are commonly components of transcription factor complexes. The bromodomain and extra-terminal (BET)-family (e.g., BRD2, BRD3, BRD4 and BRDT) share a common domain architecture comprising two N-terminal bromodomains which exhibit a high level of sequence conservation, and a more divergent C-terminal domain which is implicated in protein-protein interactions. Aberrant regulation of histone modification can affect gene activity and play a role in oncogenesis. Lysine sidechain acetylation is an important regulatory event in the function of non-histone proteins, including but not limited to Hsp90, p53, STAT transcription factors, cortactin, beta-catenin and alpha-tubulin. Thus, modulation of lysine sidechain recognition would be expected to exert important phenotypic and therapeutic effects broadly in development and disease. Despite the importance of acetyl-lysine recognition to oncogenesis, few modulators of acetyl-lysine recognition have been identified.